Factors Affecting the Response of the Maize Weevil, Sitophilus zeamais (Coleoptera: Curculionidae), to Its Aggregation Pheromone

Effects of age, dosage, starvation, crowding, and addition of 3-pentanone on response of the maize weevil, Sitophilus zeamais Motschulsky, to a mixture of its male-produced aggregation pheromone ( R*, S* )-5-hydroxy-4-methyl-3-heptanone, and the R*, R* diastereomer, were examined. Weevils ≤1 week old were attracted to pheromone, whereas 8- to 10-week-old weevils were significantly repelled by the pheromone. Weevils 1–2 days old responded to synthetic pheromone over a 1,000-fold range of doses. Starvation significantly improved response of young weevils to the pheromone, but had no effect on response by 10-week-old weevils. A trend toward better response under high-density conditions was observed in 1- to 2-day-old weevils, but not 10-week-old weevils. Males 1–2 days old were attracted to 3-pentanone, and its addition to the pheromone elicited a greater response by both sexes than response to either compound alone. Weevils 10 weeks old were strongly attracted to 3-pentanone when they had been starved. Function of the pheromone in colonization of exploitable food sources is discussed.